U.S. patent application number 10/005409 was filed with the patent office on 2002-06-27 for cleaning method, apparatus therefor, cleaning object cleaned thereby, and hopper.
Invention is credited to Hirasawa, Nobuo, Iwama, Hideo, Kowase, Hiroshi, Okazawa, Masaki, Sato, Bunryo.
Application Number | 20020082179 10/005409 |
Document ID | / |
Family ID | 18846656 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020082179 |
Kind Code |
A1 |
Okazawa, Masaki ; et
al. |
June 27, 2002 |
Cleaning method, apparatus therefor, cleaning object cleaned
thereby, and hopper
Abstract
In cleaning operation using dry ice pellets, a bridging
phenomenon of the dry ice pellets occurs. Also, static electricity
is generated, so a good cleaning effect cannot be obtained. This
invention is directed to solve these problems. In order to solve
these problems, a cleaning apparatus has a blast nozzle, a device
for pneumatically feeding a carrier gas to the blast nozzle, and a
device for supplying dry ice pellets to the blast nozzle, and
blasts a cleaning object (W) with the dry ice pellets, together
with the carrier gas, from the blast nozzle, thereby cleaning a
surface of the cleaning object (W). This cleaning apparatus
includes an air supplying device for supplying destaticizing air to
a cleaning portion of the cleaning object (W) to be cleaned by the
blast nozzle, and a charging device for charging the destaticizing
air with a polarity opposite to the polarity of the charged dry ice
pellets.
Inventors: |
Okazawa, Masaki; (Kanagawa,
JP) ; Iwama, Hideo; (Kanagawa, JP) ; Sato,
Bunryo; (Tokyo, JP) ; Kowase, Hiroshi;
(Saitama, JP) ; Hirasawa, Nobuo; (Tokyo,
JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
18846656 |
Appl. No.: |
10/005409 |
Filed: |
December 10, 2001 |
Current U.S.
Class: |
510/276 |
Current CPC
Class: |
B08B 7/02 20130101; B08B
6/00 20130101 |
Class at
Publication: |
510/276 |
International
Class: |
C11D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2000 |
JP |
378012/2000 |
Claims
What is claimed is:
1. A cleaning method characterized by comprising the steps of:
pneumatically feeding a carrier gas to a blast nozzle for cleaning
a cleaning object; supplying dry ice pellets to the blast nozzle;
blasting the cleaning object with the dry ice pellets, together
with the carrier gas, from the blast nozzle, thus cleaning a
surface of the cleaning object; and supplying air, charged with a
polarity opposite to a polarity of the charged dry ice pellets, to
a cleaning portion of a target to be blasted by the blast
nozzle.
2. The method according to claim 1, characterized by further
comprising the step of charging a cleaning operation atmosphere
with charges that cancel charges generated in the cleaning object
after collision with the dry ice pellets.
3. The method according to claim 1, characterized in that air has
charges that cancel charges generated in the cleaning object after
collision with the dry ice pellets.
4. The method according to claim 1, characterized in that air has
at least charges that cancel charges of the dry ice pellets before
collision against the cleaning object.
5. The method according to claim 4, characterized in that air is
mixed in the carrier gas immediately before being blasted from the
blast nozzle.
6. The method according to claim 3, characterized in that air is
directly supplied to the cleaning portion of the cleaning object
from a second blast nozzle separately from the carrier gas blast
nozzle.
7. The method according to claim 1, characterized in that the
carrier gas is air.
8. A cleaning apparatus which has a blast nozzle, means for
pneumatically sending a carrier gas to said blast nozzle, and means
for supplying dry ice pellets to said blast nozzle, and,blasts a
cleaning object with the dry ice pellets, together with the carrier
gas, from said blast nozzle, thereby cleaning a surface of the
cleaning object, characterized by comprising: air supplying means
for supplying air to a cleaning portion of a target to be blasted
by said blast nozzle; and charging means for charging air with a
polarity opposite to a polarity of the charged dry ice pellets.
9. The apparatus according to claim 8, characterized in that said
air supply means has a second blast nozzle for directly supplying
air to the cleaning portion of the cleaning object separately from
the carrier gas blast nozzle.
10. The apparatus according to claim 8, characterized in that said
charging means has means capable of controlling charges.
11. The apparatus according to claim 8, characterized by further
comprising second charging means for charging a cleaning operation
atmosphere with charges that cancel charges generated in the
cleaning object after collision with the dry ice pellets.
12. The apparatus according to claim 11, characterized in that said
second charging means has means capable of controlling charges.
13. A cleaning object cleaned by the cleaning method according to
claim 1.
14. A cleaning object cleaned by the cleaning apparatus according
to claim 9.
15. A hopper for reserving dry ice pellets which are blasted,
together with a carrier gas, from a blast nozzle to a cleaning
object, so as to clean a surface of the cleaning object,
characterized by comprising agitating means for agitating the dry
ice pellets, thereby preventing bridging of the dry ice
pellets.
16. The hopper according to claim 15, characterized in that said
agitating means has an agitation rotating shaft with a distal end
projecting into the hopper, an agitation blade attached to the
distal end of the agitation rotating shaft, and a driving source
connected to a proximal end of the agitation rotating shaft to
rotatably drive the agitation rotating shaft.
17. The hopper according to claim 16, characterized in that the
agitation rotating shaft includes a plurality of agitation rotating
shafts arranged with directions different from each other.
18. The hopper according to claim 16, characterized in that one
agitation blade is arranged at a lower end of the hopper.
19. The hopper according to claim 16, characterized in that said
agitating means further has means capable of controlling a
rotational speed of the agitation rotating shaft.
20. The hopper according to claim 15, characterized in that said
agitating means has at least one agitation rod with a distal end
projecting into the hopper, an agitation arm attached to the distal
end of the agitation rod, and a driving source connected to a
proximal end of the agitation rod to reciprocally move the
agitation rod in a longitudinal direction thereof.
21. The hopper according to claim 20, characterized in that said
agitating means further has means capable of controlling a moving
speed of the agitation rod.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a cleaning method of
cleaning a surface of a cleaning object by blasting the cleaning
object with dry ice pellets from a blast nozzle together with a
carrier gas, and an apparatus for the same.
[0002] The present also relates to a cleaning object cleaned by the
cleaning method and apparatus, and a hopper for reserving the dry
ice pellets.
BACKGROUND OF THE INVENTION
[0003] A need for reusing or so-called recycling the constituent
components and units of business and electric devices has become
strong in terms of effective utilization of resources,
countermeasure for environmental pollution, and the like.
[0004] To recycle the constituent components and units of various
types of devices, they must be removed from the devices, and
whether they function correctly must be checked. Also, these
components and units must be maintained in or restored to an almost
brand-new state.
[0005] In practice, as these devices are used, they are soiled or
contaminated in the atmosphere where they have been used, and
cleaning operation is needed to remove their soil and
contamination. For example, regarding a copying machine or printer
as an example of a business device, as it uses toner as the image
forming material, soil or contamination due to toner dust attaches
to, e.g., the fixing unit and components around it. In these
devices, a printed wiring board having a built-in electrical
circuit for electricity control is mounted. Such printed wiring
board is contaminated by dust accumulated by static
electricity.
[0006] Regarding electric home appliances including an air
conditioner such as a cooler, a television, and a refrigerator,
regulations for recycling electric home appliances have been put
into operation. A recycling system is also needed for other home
electrical appliances including information devices such as a
personal computer, business devices such as a printer, or other
industrial devices in terms of the environmental and resources
problems.
[0007] To cope with this demand of recycling the electric
appliances, a technique for causing granular dry ice, i.e., dry ice
pellets, as a cleaning agent to impinge on a surface to be cleaned,
thereby removing a substance attaching to the surface to be cleaned
is disclosed in, e.g., Japanese Patent Laid-Open No. 61-15749.
Japanese Patent Laid-Open No. 10-202210 discloses a cleaning system
for automatically carrying out the cleaning operation of a
recycling component while preventing it from being damaged.
[0008] The techniques disclosed in the above references disclose a
system for removing soil of a recycling component of an OA (Office
Automation) device by blasting it with dry ice pellets. Cleaning
operation is performed by moving a blast nozzle, which blasts the
dry ice pellets together with pressurized air as a carrier gas,
along the surface of the recycling component as a cleaning
object.
[0009] Japanese Patent Laid-Open No. 10-202208 discloses a
technique for performing cleaning operation by using solid pellets
such as dry ice pellets as a cleaning agent. Also, Japanese Patent
Laid-Open No. 51-60095 is known as a cleaning technique with a sand
blast method using a sublimation material.
[0010] The various types of electrical products described above
have a built-in printed wiring board mounted with electronic
components. To meet the demand for recycling by disassembling and
cleaning these products, a countermeasure against static
electricity must be taken for these electronic components.
[0011] When cleaning the surface of a cleaning object by blasting
it with dry ice pellets, the dry ice pellets are blasted, together
with a carrier gas, from a hopper for reserving the dry ice pellets
toward the cleaning surface of the cleaning object by a blast
nozzle. When the dry ice pellets are conveyed in a supply pipe path
at a high speed from the hopper to the blast nozzle, they may be
electrostatically charged by mutual friction during conveyance and
friction with the inner wall of a flexible pipe that forms the
supply pipe path. Since the cleaning object is blasted with charged
dry ice, the cleaning object itself is electrostatically charged.
Accordingly, dust attaches again to the cleaning object after
cleaning, and sometimes a good cleaning effect cannot be obtained.
Also, a person in charge of cleaning operation himself may be
electrified by static electricity.
[0012] Furthermore, when the cleaning object has a built-in printed
wiring board mounted with electronic components and the like, the
electronic components and the like are damaged by static
electricity described above. Then, the cleaning object cannot be
reused.
SUMMARY OF THE INVENTION
[0013] It is an object of the present invention to provide a
cleaning method which is not adversely affected by static
electricity generated by cleaning operation, an apparatus for the
same, and a cleaning object cleaned by them.
[0014] It is another object of the present invention to provide a
hopper for reserving dry ice pellets which are blasted, together
with a carrier gas, from a blast nozzle toward the cleaning object
in order to clean the surface of the cleaning object, without
causing a bridging phenomenon.
[0015] According to the first aspect of the present invention,
there is provided a cleaning method characterized by comprising the
steps of pneumatically feeding a carrier gas to a blast nozzle for
cleaning a cleaning object, supplying dry ice pellets to the blast
nozzle, blasting the cleaning object with the dry ice pellets,
together with the carrier gas, from the blast nozzle, thus cleaning
a surface of the cleaning object, and supplying air, charged with a
polarity opposite to a polarity of the charged dry ice pellets, to
a cleaning portion of a target to be blasted by the blast
nozzle.
[0016] According to the present invention, when the dry ice pellets
are blasted, together with the carrier gas, from the blast nozzle
to the cleaning object, soil attaching to the surface of the
cleaning object is blown off by the collision force generated by
blasting operation and the pressure of expansion accompanying
sublimation of the dry ice pellets. In this case, when supplying
the dry ice pellets to the blast nozzle, static triboelectricity is
generated. When air charged with a polarity opposite to the
polarity of the static triboelectricity of the charged dry ice
pellets is supplied to the cleaning portion of the cleaning object,
the charged state of the dry ice pellets is electrically
neutralized. As a result, an inconvenience that soil blown off from
the surface of the cleaning object reattaches to the surface of the
cleaning object due to the static electricity of the dry ice
pellets can be prevented.
[0017] According to the second aspect of the present invention,
there is provided a cleaning apparatus which has a blast nozzle,
means for pneumatically feeding a carrier gas to the blast nozzle,
and means for supplying dry ice pellets to the blast nozzle, and
blasts a cleaning object with the dry ice pellets, together with
the carrier gas, from the blast nozzle, thereby cleaning a surface
of the cleaning object, characterized by comprising air supplying
means for supplying air to a cleaning portion of a target to be
blasted by the blast nozzle, and charging means for charging air
with a polarity opposite to a polarity of the charged dry ice
pellets.
[0018] According to the present invention, when the carrier gas is
pneumatically fed to the blast nozzle and the dry ice pellets are
supplied to the blast nozzle, the dry ice pellets are blasted,
together with the carrier gas, from the blast nozzle to the
cleaning object. Soil attaching to the surface of the cleaning
object is blown off by the collision force generated by blasting
operation and the pressure of expansion accompanying sublimation of
the dry ice pellets. In this case, when supplying the dry ice
pellets to the blast nozzle, static triboelectricity is generated.
When air is charged with a polarity opposite to the polarity of the
static triboelectricity of the charged dry ice pellets and is
supplied to the cleaning portion of the cleaning object, the
charged state of the dry ice pellets is electrically neutralized.
As a result, an inconvenience that soil-blown off from the surface
of the cleaning object reattaches to the surface of the cleaning
object due to the static electricity of the dry ice pellets can be
prevented.
[0019] According to the third aspect of the present invention,
there is provided a cleaning object cleaned by the cleaning method
according to the first aspect of the present invention, or cleaned
by using the cleaning apparatus according to the second aspect of
the present invention. Such cleaning object is also incorporated in
the scope of the present invention.
[0020] According to the fourth aspect of the present invention,
there is provided a hopper for reserving dry ice pellets which are
blasted, together with a carrier gas, from a blast nozzle to a
cleaning object, so as to clean a surface of the cleaning object,
characterized by comprising agitating means for agitating the dry
ice pellets, thereby preventing bridging of the dry ice
pellets.
[0021] According to the present invention, the dry ice pellets
reserved in the hopper are agitated by the agitating means. Thus,
the bridging phenomenon that the dry ice pellets fuse with each
other by sublimation of part of the dry ice pellets is
prevented.
[0022] Other objects and advantages besides those discussed above
shall be apparent to those skilled in the art from the description
of a preferred embodiment of the invention which follows. In the
description, reference is made to accompanying drawings, which form
a part hereof, and which illustrate an example of the invention.
Such example, however, is not exhaustive of the various embodiments
of the invention, and therefore reference is made to the claims
which follow the description for determining the scope of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective view showing the outer appearance of
a fixing unit in a copying machine as an example of a cleaning
object as the target of the present invention;
[0024] FIG. 2 is a mechanical illustration showing the schematic
structure of a cleaning apparatus according to an embodiment of the
present invention that can realize a cleaning method according to
the present invention;
[0025] FIG. 3 is an extracted enlarged view showing the outer
appearance of a cleaning gun portion having a built-in blast nozzle
in the embodiment shown in FIG. 2;
[0026] FIG. 4 is a sectional view showing the schematic structure
of a hopper portion in the embodiment shown in FIG. 2;
[0027] FIG. 5 is a sectional view taken along the line V-V of FIG.
4 in a state from which an agitating means is omitted;
[0028] FIG. 6 is an illustration of a hopper according to another
embodiment of the present invention;
[0029] FIG. 7 is an illustration of a hopper according to still
another embodiment of the present invention;
[0030] FIG. 8 is an illustration of a hopper according to a
different embodiment of the present invention;
[0031] FIG. 9 is an illustration of a hopper according to still
another embodiment of the present invention;
[0032] FIG. 10 is an illustration of a hopper according to still
another embodiment of the present invention; and
[0033] FIG. 11 is an illustration of a hopper according to still
another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] A cleaning method according to the first embodiment of the
present invention can also comprise the step of charging a cleaning
operation atmosphere with charges that cancel charges generated in
the cleaning object after collision with the dry ice pellets.
[0035] Air can have charges that cancel charges generated in the
cleaning object after collision with the dry ice pellets. This air
can be directly supplied to the cleaning portion of the cleaning
object from a second blast nozzle separately from the carrier gas
blast nozzle.
[0036] Alternatively, air may at least have charges that cancel
charges of the dry ice pellets before collision against the
cleaning object. In this case, air can be mixed in the carrier gas
immediately before being blasted from the blast nozzle.
[0037] The carrier gas can be air.
[0038] In a cleaning apparatus according to the second embodiment
of the present invention, an air supply means may have a second
blast nozzle for directly supplying air to the cleaning portion of
the cleaning object separately of a carrier gas.
[0039] A charging means can have a means capable of controlling
charges.
[0040] The apparatus can also have a second charging means for
charging a cleaning operation atmosphere with charges that cancel
charges generated in the cleaning object after collision with the
dry ice pellets. In this case, the second charging means can have a
means capable of controlling charges.
[0041] In a hopper according to the fourth embodiment of the
present invention, an agitating means can have an agitation
rotating shaft with a distal end projecting into the hopper, an
agitation blade attached to the distal end of the agitation
rotating shaft, and a driving source connected to the proximal end
of the agitation rotating shaft to rotatably drive the agitation
rotating shaft. In this case, a plurality of agitation rotating
shafts may be arranged with directions different from each other.
One agitation blade is preferably arranged at the lower end of the
hopper. Alternatively, the agitating means may also have a means
capable of controlling the rotational speed of the agitation
rotating shaft.
[0042] The agitating means can have at least one agitation rod with
a distal end projecting into the hopper, an agitation arm attached
to the distal end of the agitation rod, and a driving source
connected to the proximal end of the agitation rod to reciprocally
move the agitation rod in its longitudinal direction. In this case,
the agitating means can further have a means capable of controlling
the moving speed of the agitation rod.
[0043] Embodiments in which the present invention is applied to a
fixing unit in a copying machine will be described in detail with
reference to FIGS. 2 to 11. The present invention is not limited to
these embodiments. These embodiments may be combined, and the
present invention can be applied to other techniques to be
incorporated in the scope of the present invention described in the
appended claims of this specification.
[0044] The cleaning object in this embodiment is a fixing unit W in
a copying machine as shown in FIG. 1. The fixing unit W has a feed
section W1 to which a toner-developed copy sheet is transferred
from a developing unit (not shown), a fixing section W3 for fixing
the toner image of the copy sheet fed from the feed section W1
through a convey section W2, a delivery section W4 for delivering
the copy sheet with the fixed toner image from the convey section
W2 to the outside of the fixing unit W, a driving system W5 for
driving the feed section W1, convey section W2, fixing section W3,
and delivery section W4, a controller (not shown) for controlling
the operation of the driving system W5, and a frame W6 to which the
feed section W1, convey section W2, fixing section W3, delivery
section W4, driving system W5, and controller are attached. In the
copying machine, various types of units in the copying machine are
soiled or contaminated in accordance with the frequency they are
used and the atmosphere where they are used. The soil or
contamination is caused by various factors, e.g., soil caused by
scattering of the toner accommodated in the copying machine, soil
accompanying scattering of the toner, which occurs while the units
are being repaired or maintained, or dust attracted and attached by
the static electricity generated in the electrical circuits formed
in the respective units.
[0045] FIG. 2 shows the schematic structure of a cleaning apparatus
according to this embodiment. The interior of a housing 11
is-partitioned by a partition 12 into a cleaning booth 13 and
supply/recovery booth 14. The housing 11 has an opening/closing
door 15 openable to load or unload the fixing unit W in or from the
cleaning booth 13, and a supply/delivery table 16 which, when
loading/unloading the fixing unit W, can move upward from the state
indicated by a solid line in FIG. 2 to the same height as that of
the floor surface of the cleaning booth 13, to improve the
operability of the loading/unloading operation. Also, a transparent
window (not shown) through which the operator observes the interior
of the cleaning booth 13, and a glove box (not shown) for allowing
the operator to operate a cleaning gun 17 in the cleaning booth 13
from the outside of the cleaning booth 13 are formed on that side
wall portion of the housing 11 which forms the cleaning booth
13.
[0046] A illumination device 18 which allows observing operation
state from the outside through the window described above is
provided to the cleaning booth 13. A rotary table 19, to which the
fixing unit W is removably fixed with a predetermined posture, is
provided to the cleaning booth 13 to be rotatable about a vertical
axis. The rotary table 19 is rotatably driven by a table driving
motor 20. The cleaning gun 17 with a blast nozzle 21 for blasting,
together with a carrier gas, dry ice pellets for cleaning the
fixing unit W is suspended in the cleaning booth 13 by using a
hoist (not shown) or the like. The operator can manually operate
the position and posture of the cleaning gun 17 from the outside of
the cleaning booth 13 through the glove box.
[0047] FIG. 3 shows the outer appearance of the cleaning gun 17
portion of this embodiment. A flexible carrier gas supply pipe 22
and pellet supply pipe 23 are connected to the cleaning gun 17. The
cleaning gun 17 has the blast nozzle 21 for blasting the dry ice
pellets together with the carrier gas toward the fixing unit W, and
a trigger 24 to be operated by the operator for adjusting the blast
state of the carrier gas from the blast nozzle 21. The dry ice
pellets supplied to the cleaning gun 17 are drawn out from the
pellet supply pipe 23 by a negative pressure generated by the
carrier gas flowing in the cleaning gun 17. The dry ice pellets,
together with the carrier gas, are blown off from the blast nozzle
21 to the fixing unit W at a high speed.
[0048] The flexible carrier gas supply pipe 22 and pellet supply
pipe 23 are connected to a stationary carrier gas supply pipe 25
and stationary pellet supply pipe 26, which are fixed to the
supply/recovery booth 14, through joints 27 and 28 formed on the
partition 12, so they are suspended, together with the cleaning gun
17, from the housing 11 in the cleaning booth 13. To form the
pellet supply pipe 23 in the cleaning booth 13, a flexible piping
material with excellent corrosion resistance and low-temperature
brittleness, e.g., a Teflon (polytetrafluoroethylene) tube with an
inner diameter of 13 mm and an outer diameter of 16 mm and
available from Du Pont, must be used, and a metal pipe such as one
used to form the stationary pellet supply pipe 26 cannot be used.
Therefore, due to the friction of the dry ice pellets moving in the
pellet supply pipe 23 at a speed of, e.g., 100 m to 180 m
(preferably 150 m) per second and friction between the dry ice
pellets and the inner wall of the pellet supply pipe 23, the dry
ice pellets are sometimes undesirably electrostatically charged
with negative (or positive) electricity. The present invention
solves this inconvenience.
[0049] A lamp 29, provided in addition to the illumination device
18 fixed in the cleaning booth 13, for illuminating the working
portion, an air blow-off nozzle 30 for blowing off destaticizing
air to that portion of the fixing unit W which is to be blasted by
the blast nozzle 21, and a charger 31 for charging destaticizing
air blown off from the air blow-off nozzle 30 with the opposite
polarity (positive in this embodiment) to the polarity of the
charged dry ice pellets are mounted in the cleaning gun 17. A
flexible destaticizing air supply pipe 32 is connected to the air
blow-off nozzle 30 and suspended, together with the carrier gas
supply pipe 22 and the like, from the housing 11 in the cleaning
booth 13, and is connected to a stationary destaticizing air supply
pipe 33, fixed to the supply/recovery booth 14, through a joint 34
formed on the partition 12.
[0050] In this embodiment, the air blow-off nozzle 30 is arranged
in parallel with the blast nozzle 21. Alternatively, destaticizing
air may be supplied into the blast nozzle 21. It is also effective
to blow off a detergent, together with the carrier gas, dry ice
pellets, and destaticizing air, from the cleaning gun 17 to the
cleaning portion of the fixing unit so that the cleaning effect for
the fixing unit W is improved.
[0051] In this embodiment, as the carrier gas, air from an air
compressor (not shown) serving as the same air supply source as for
destaticizing air is used. Pressurized air is supplied from the air
compressor arranged outside the housing 11 to the stationary
carrier gas supply pipe 25 and stationary destaticizing air supply
pipe 33 through a joint 35 formed on the housing 11. Pressure
adjustment devices 36 and 37 for reducing the pressures of the
carrier gas and destaticizing air to predetermined pressures, and
opening/closing solenoid valves 38 and 39 for performing switching
operation between supply and discharge of the carrier gas and
destaticizing air, are formed midway along the stationary carrier
gas supply pipe 25 and stationary destaticizing air supply pipe
33.
[0052] A hopper 40 for reserving about 30 liters of dry ice pellets
each forming a round rod with, e.g., a diameter of 3 mm and a
length of about 3 mm to 10 mm, a feeder 41 arranged immediately
under the hopper 40 to feed out the dry ice pellets in the hopper
40 to the stationary pellet supply pipe 26, a dust removing device
42 for removing toner particles and dust blown away from the fixing
unit W by the cleaning gun 17, and a recovery device 43 for
recovering carbon dioxide are formed in the supply/recovery booth
14.
[0053] FIG. 4 shows the enlarged sectional structure of the hopper
40 of this embodiment, and FIG. 5 shows its sectional structure
taken along the line V-V. More specifically, the feeder 41 with a
screw 48 rotated by a feed driving motor 47 is arranged at the
lower end of the hopper 40 covered by a heat insulation wall 44 and
an openable heat insulation lid 46 through a seal member 45. The
feeder 41 conveys the dry ice pellets from the lower end of the
hopper 40 to the stationary pellet supply pipe 26. A sensor 49 for
detecting the presence/absence of the dry ice pellets moving in the
stationary pellet supply pipe 26, an opening/closing valve 50 for
performing switching operation between supply and discharge of the
dry ice pellets, a crusher (not shown) for crushing the dry ice
pellets further finely to, e.g., a diameter of 0.5 mm or less and a
length of 2 mm or less, and the like are interposed midway along
the stationary pellet supply pipe 26. When the opening/closing
valve 50 operated by an actuator 51 opens/closes the path of the
stationary pellet supply pipe 26, supply and discharge of the dry
ice pellets to and from the cleaning gun 17 are controlled.
[0054] An upwardly tilted first agitation rotating shaft 52 is
rotatably attached to the lower end of the hopper 40. A first blade
driving motor 53 is connected to the proximal end of the first
agitation rotating shaft 52 and rotatably drives it at a low speed
of, e.g., about 5 rpm. A first agitation blade 54 is integrally
fixed to the distal end of the first agitation rotating shaft 52
located in the hopper 40, to agitate the dry ice pellets located at
the lower end of the hopper 40, thereby preventing bridging of the
dry ice pellets. The first agitation blade 54 has such a blade
shape that it can agitate the dry ice pellets in the entire lower
end of the hopper 40 as much as possible. A second blade driving
motor 56 is mounted on the heat insulation lid 46 having a built-in
relief valve 55. The second blade driving motor 56 is connected to
the upper end of a vertical second agitation rotating shaft 58.
Second agitation blades 57 formed of a wire project radially from
the second agitation rotating shaft 58 at an angular distance of
180.degree.. When the second blade driving motor 56 is actuated and
the second agitation rotating shaft 58 is rotated at a low speed
of, e.g., about 9 rpm, the dry ice pellets located at the center of
the hopper 40 are agitated, so they are prevented from causing
bridging. Therefore, in this embodiment, the agitation rotating
shafts 52 and 58, agitation blades 54 and 57, driving motors 53 and
56, and the like apparently make up the agitating means of the
present invention.
[0055] If the urging force of the agitation blades 54 and 57
against the dry ice pellets increases, sublimation of the dry ice
pellets progresses, and bridging undesirably tends to occur easily.
Hence, the first and second agitation rotating shafts 52 and 58
need not be rotated at high speeds. Also, consideration must be
made so the rotational resistances of the agitation blades 54 and
57 against the dry ice pellets do not become excessively large.
[0056] In this embodiment, a vibrator 59 for vibrating the hopper
40 at a low frequency is mounted on the outer wall of the hopper 40
in order that the inner wall of the hopper 40 and the dry ice
pellets are prevented from being fixed to each other.
[0057] The lower end of the cleaning booth 13 and the dust removing
device 42 communicate with each other through a suction pipe 60.
The dust removing device 42 in this embodiment has an exhaust
blower 61 for drawing by suction a gas and the like in the cleaning
booth 13 through the suction pipe 60, a blower driving motor 62 for
rotatably driving the exhaust blower 61, a dust tank 63 for
reserving comparatively heavy toner particles and dust by utilizing
gravity, and a filter 64 for catching fine particles that did not
fall into the recovery pipe 63. The filter 64 and dust tank 63 can
be exchanged when necessary. A recovery device 43 for recovering
carbon dioxide passing through the filter 64 is incorporated
between the filter 64 and exhaust blower 61.
[0058] The recovery device 43 of this embodiment has a membrane 66
which is rotated by a membrane driving motor 65 at a predetermined
speed, and a recovery pipe 67 for recovering carbon dioxide caught
by the membrane 66. The recovery pipe 67 is extended outside the
housing 11 and is guided to a dry ice manufacturing device (not
shown).
[0059] Air which has passed through the exhaust blower 61 and from
which carbon dioxide is recovered is mostly exhausted outside the
housing 11, and is then partly returned to the cleaning booth 13
through an ionizer 68. The ionizer 68 electrostatically charges air
passing through it by an RF power supply 69. In this embodiment,
the atmosphere of the cleaning booth 13 is electrostatically
charged to be slightly positive (or negative), so charges formed by
negative (or positive) static electricity generated in the fixing
unit W after collision with the dry ice pellets are canceled.
[0060] Therefore, charges formed by the charger 31 suffice as far
as they cancel the charges of the dry ice pellets before colliding
against the cleaning portion of the fixing unit W.
[0061] It is confirmed by the experiment performed by the present
inventors that, if the charged state of the dry ice pellets cannot
be correctly grasped, electrostatic charging of the fixing unit W
can be neutralized to a certain degree by performing control
operation of switching the polarity of charged air blown off from
the air blow-off nozzle 30 and ionizer 68 at every predetermined
period of time. A method of alternately blowing off positive
charged air and negative charged air in a switching manner to the
cleaning surface of the cleaning object is also incorporated in the
present invention. This method is effective probably because
excessive charged particles are continuously discharged, together
with air and carbon dioxide, from the suction pipe 60 to the
outside of the cleaning booth 13.
[0062] The driving motors 20, 47, 53, 56, 62, and 65,
opening/closing solenoid valves 38 and 39, actuator 51, vibrator
59, and the like are driven in an interlocked manner, when
necessary, by a control device 70 with an operating portion (not
shown) formed at the upper end of the housing 11 and operable by
the operator.
[0063] Since the controller of the fixing unit W has a built-in
printed wiring board with electronic components (not shown) and the
like mounted thereon, it must be prevented from being damaged by
static electricity during cleaning operation. According to the
present invention, the dry ice pellets blasted in the charged state
from the cleaning gun 17 are electrically neutralized by charged
air with the opposite polarity, and electrostatic charging
accompanying collision of the dry ice pellets against the fixing
unit is also neutralized simultaneously. Therefore, damages caused
by static electricity to the printed wiring board and the like of
the controller can be prevented reliably.
[0064] The above embodiment describes the agitating means in which
the two second agitation blades 57 with different lengths in the
radial direction project from the second agitation rotating shaft
58. Any agitating means other than that of this embodiment, e.g.,
one with one of the arrangements shown in FIGS. 6 to 11
schematically showing other embodiments of the agitating means, can
naturally be employed as far as it can prevent bridging of the dry
ice pellets in the hopper 40.
[0065] In these embodiments, the elements with the same functions
as those of the above embodiment are denoted by the same reference
numerals, and a repetitive description thereof will be omitted.
More specifically, in the agitating means shown in FIG. 6, a pair
of frame-like second agitation blades 57 are attached to a second
agitation rotating shaft 58 to be vertically spaced apart from each
other with an angular interval of 180.degree.. This can reliably
prevent bridging of the dry ice pellets throughout the entire
vertical range of a hopper 40. In an agitating means of the
embodiment shown in FIG. 7, a plurality of (two in the embodiment
shown in FIG. 7) second agitation rotating shafts 58 are vertically
arranged. In this embodiment, second agitation blades 57 of one
second agitation rotating shaft 58 are shifted from second
agitation blades 57 of the other second agitation rotating shaft 58
in the vertical direction. Thus, the two second agitation rotating
shafts 58 can be arranged close to each other.
[0066] In the embodiment shown in FIG. 8, a second agitation blade
57 of a second agitation rotating shaft 58 is spirally formed. The
second agitation rotating shaft 58 can be rotated in the forward
and reverse directions regardless of the spiral direction of the
second agitation blade 57. In this case, a gap 71 is formed between
the circumferential surface of the second agitation rotating shaft
58 and the inner side of the second agitation blade 57 so an
excessively large contact pressure is not generated between the
second agitation blade 57 and dry ice pellets. The second agitation
blade 57 floats above the second agitation rotating shaft 58, while
its upper and lower ends are fixed to the second agitation rotating
shaft 58. In the embodiment shown in FIG. 9, at least one (two in
the embodiment shown in FIG. 9) second agitation rotating shaft 58
is rotatably attached to a hopper 40 such that its axis becomes
horizontal. In the embodiment shown in FIG. 9, second agitation
blades 57 of a lower second agitation rotating shaft 58 are located
between second agitation blades 57 of an upper second agitation
rotating shaft 58. Thus, the two second agitation rotating shafts
58 can be arranged close to each other. In the agitating means
shown in FIG. 10, a second agitation rotating shaft 58 is rotatably
attached to a hopper 40 to be inclined with respect to the hopper
40, so that its axis is perpendicular to the axis of a first
agitation rotating shaft 52. In the agitating means shown in FIG.
11, at least one (two in the embodiment shown in FIG. 11) agitation
rod 73 extends in the horizontal direction. The proximal end of the
agitation rod 73 is connected to an actuator (not shown), e.g., a
hydraulic cylinder or an electrical motor through a crank mechanism
or rack-and-pinion mechanism, and an agitation arm 72 radially
projects from that distal end of the agitation rod 73 which is
located in a hopper 40. The agitation rod 73 is reciprocally moved
in the horizontal direction, thereby agitating dry ice pellets in
the hopper 40. The direction of the agitation rod 73 is not limited
to the horizontal direction, but can be vertical or be inclined as
shown in FIG. 10.
[0067] The cleaning method of the embodiments described above has
the step of supplying air, charged with the opposite polarity to
the charged polarity of the dry ice pellets, to the cleaning
portion of the blast target which is to be blasted with the blast
nozzle. Therefore, static electricity generated in the dry ice
pellets can be destaticized reliably. Thus, static electricity is
prevented from being generated in the cleaning object by static
electricity of the dry ice pellets, and a good cleaning effect can
be obtained.
[0068] If the cleaning method further has the step of charging the
cleaning operation atmosphere with charges that cancel charges
generated in the cleaning object after collision with the dry ice
pellets, static electricity generated when the dry ice pellets
collide against the cleaning object can also be reliably
neutralized. Thus, an inconvenience that dust reattaches to the
cleaning object after cleaning can be prevented.
[0069] If air has charges that cancel charges generated in the
cleaning object after collision with the dry ice pellets, static
electricity generated when the dry ice pellets collides against the
cleaning object can also be neutralized reliably. Thus, an
inconvenience that that reattaches to the cleaning object after
cleaning can be prevented.
[0070] If air has at least charges that cancel the charges of the
dry ice pellets before collision against the cleaning object,
static electricity generated in the dry ice pellets can be
destaticized reliably. Thus, static electricity is prevented from
being generated in the cleaning object by static electricity of the
dry ice pellets.
[0071] When air is mixed in the carrier gas immediately before
being blasted from the blast nozzle, contact of the dry ice pellets
in the charged state and air charged with the opposite charged
state to that of the dry ice pellets is promoted, so the dry ice
pellets can be destaticized more reliably.
[0072] When air is directly supplied to the cleaning portion of the
cleaning object from the second blast nozzle separately from the
carrier gas blast nozzle, destaticizing air can be reliably blown
off only to a portion where static electricity is generated when
being collided with the dry ice pellets, and only the charged
portion can be destaticized reliably.
[0073] When the carrier gas is air, any special carrier gas need
not be used, and the running cost can be reduced.
[0074] The cleaning apparatus according to the present invention
has an air supplying means for supplying air to a cleaning portion
of a target to be blasted by the blast nozzle, and a charging means
for charging air with a polarity opposite to a polarity of the
charged dry ice pellets. Static electricity generated in the dry
ice pellets can be destaticized reliably, and static electricity is
prevented from being generated in the cleaning object by static
electricity of the dry ice pellets. Thus, a good cleaning object
can be obtained.
[0075] If the air supply means has a second blast nozzle for
directly supplying air to the cleaning portion of the cleaning
object separately from the carrier gas blast nozzle, destaticizing
air can be reliably blown off only to a portion where static
electricity is generated upon collision with the dry ice pellets.
Thus, only the charged portion can be reliably destaticized.
[0076] When the charging means has a means capable of controlling
charges, it can impart air with optimal charges in accordance with
the charges of the dry ice pellets or the like. Thus, generated
static electricity can be destaticized reliably.
[0077] When a second charging means is further provided which
charges a cleaning operation atmosphere with charges that cancel
charges generated in the cleaning object after collision with the
dry ice pellets, it can also reliably neutralize static electricity
generated when the dry ice pellets collide against the cleaning
object. Thus, an inconvenience that dust reattaches to the cleaning
object after cleaning can be prevented.
[0078] When the second charging means has a means capable of
controlling charges, charges of the cleaning operation atmosphere
can be controlled in the optimal manner in units of individual
cleaning objects. Thus, static electricity generated in each
cleaning object can be destaticized reliably.
[0079] According to the cleaning object of the above embodiment,
since static electricity generated during cleaning operation is
removed, reattaching of dust due to static electricity after
cleaning operation can be prevented.
[0080] The hopper according to the above embodiment has an
agitating means for agitating the dry ice pellets, thereby
preventing bridging of the dry ice pellets. Thus, a bridging
phenomenon of the dry ice pellets in the hopper can be prevented,
and the dry ice pellets reserved in the hopper can be smoothly fed
out toward the blast nozzle.
[0081] When a plurality of agitation rotating shafts are arranged
with directions different from each other, the agitating effect of
the dry ice pellets in the hopper can be improved, so the bridging
phenomenon of the dry ice pellets can be prevented more
reliably.
[0082] When one agitation blade is arranged at a lower end of the
hopper, the bridging phenomenon of the dry ice pellets located at
the lower end of the hopper can be prevented reliably. Thus, the
dry ice pellets can be smoothly fed out from the lower end of the
hopper to the blast nozzle.
[0083] When the agitating means further has a means capable of
controlling the rotational speed of the agitation rotating shaft,
the interior of the hopper can be agitated with an optimal
rotational speed in accordance with the state of the dry ice
pellets and the like. Thus, the bridging phenomenon of the dry ice
pellets can be prevented more reliably.
[0084] When the agitating means further has a means capable of
controlling the moving speed of the agitation rod, the interior of
the hopper can be agitated with an optimal moving speed in
accordance with the state of the dry ice pellets and the like.
Thus, the bridging phenomenon of the dry ice pellets can be
prevented more reliably.
[0085] The present invention is not limited to the above
embodiments and various changes and modifications can be made
within the spirit and scope of the present invention. Therefore, to
apprise the public of the scope of the present invention the
following claims are made.
* * * * *